For clarity, the present invention will be described in relation to a digging implement including a slide hammer. It will however be obvious to those skilled in the art that the method of attachment described is equally applicable to any driven implement having a head attached to a shaft. It will also be apparent that the attachment method is equally applicable to non-driven implement including a shaft and a tool portion.
Digging implements for working in tough materials such as frozen or stony ground or where tough root structures need to be severed are well known.
Slide hammer assisted digging tools are one such well known implement. The slide hammer allows the user to apply extremely high energy impulses to drive a tool portion such as an implement head through tough materials, typically the implement head will be a spade head or similar type blade.
One disadvantage associated with impact driven implements is that the impact action that provides the impetus to drive the implement head through tough materials, also applies very high shock loading to the attachment means holding the head of the implement to the shaft, such as welds, resulting in rapid failure if the implement is frequently used to dig through tough materials.
Improved durability can be obtained by using re-enforced welds and large weld surface areas. The disadvantage of such a methodology is that the welds typically run longitudinally to the handle, the majority of the weld thereby being subjected to longitudinal sheer stress. It is well known in the art that welds running longitudinally to the line of applied force are substantially less strong than welds running transversely to the line of applied force. The available contact area of the shaft capable of being welded to the implement head and transversely to the line of applied force, is therefore limited. Unless the durability or functionality of the implement is compromised in terms of strength or in terms of having an implement that will penetrate through tough materials and not be impeded by large block like welds.
It is therefore the purpose of the present invention to provide a digging implement which provides the advantages of an impact drive, but includes a novel construction methodology which results in an implement that is more robust to repetitive use in hard conditions.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
Throughout this specification, the word “comprise”, or variations thereof such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.